I had this issue earlier and it ended up being on the google calendar side of things. You need your calendar to be set as public for it to work.but Go to your calendar > calendar settings > share calendar and check the ‘set this calendar to public’ box THEN (this is the part that I missed initially) make sure the dropdown menu next to it is on “see all event details” instead of “see only free/busy (hide details)”. Then clear the cache on your simple calendar and it should work—or at least that’s how I did it.
Hope that helps!
